Which type of electromagnetic energy is invisible to the human eye?

• A. Visible spectrum
• B. Ultraviolet
• C. Prism
• D. Filter

Answer: (B)

The idea here is understanding which part of the electromagnetic spectrum our eyes can’t detect. Ultraviolet light has wavelengths shorter than violet light, so it lies outside what our eyes can see. Because of this, ultraviolet energy is invisible to us, even though it’s a real form of electromagnetic energy and can interact with materials and living tissue (like causing sunburn).

A prism is a tool that splits light into its component colors; it isn’t a type of energy, just a way to study light. A filter is something that blocks or passes certain wavelengths; it changes what we can see but isn’t itself a form of energy. The visible spectrum is the range we can see with our eyes, so that energy is visible, not invisible.